On July 18, 1926, Billy Southworth led the Cardinals to a 9-7 victory over the Phillies with a walk off blast at Sportsman's Park in St. Louis. The Cardinals had led 6-3 in this one after four innings, before the Phillies took the lead with a four run sixth. The Cardinals answered back with a run in the seventh to tie it up, which stood until the ninth, when Wayland Dean walked Rogers Hornsby to set the table for Southworth, who parked one in the seats to win it. The 33-year-old future skipper had come over to the Cardinals in mid June as a part of a trade with the New York Giants. He went onto become a key piece to that championship puzzle by hitting .317 in 99 games for the Redbirds, before hitting .345 in the Fall Classic, which included several clutch hits that brought St. Louis their first championship title in the modern era. Many years later Southworth would guide the club to two championship titles.
You can read all about the life and times of Billy Southworth here:
Check out the box score here: http://www.baseball-reference.com/boxes/SLN/SLN192607180.shtml